glsl/glcpp: Add support for comments between #define and macro identifier

glsl/glcpp: Add support for comments between #define and macro identifier

The recent adddition of an error for "#define followed by a non-identifier"
was a bit to aggressive since it used a regular expression in the lexer to
flag any character that's not legal as the first character of an identifier.

But we need to allow comments to appear here, (since we aren't removing
comments in a preliminary pass). So we refine the error here to only flag
characters that could not be an identifier, nor a comment, nor whitespace.

We also augment the existing comment support to be active in the <DEFINE>
state as well.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>